System and method for media stream indexing and synchronization

ABSTRACT

An indexing system and method for allowing a viewer to control the mode of delivery of program material. By mapping from time to data position, data delivery can begin at any selected time in the program material. The indexing method also provides for controlling data delivery to begin at the beginning of a frame of data. A synchronizing method is provided to minimize a time offset between audio and video data, particularly in environments using groups of pictures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/219,341 filed 2 Sep. 2005 and now U.S. Pat. No. 7,272,780 whichissued 18 Sep. 2007; and which application is a continuation of U.S.patent application Ser. No. 10/677,581 filed Oct. 1, 2003 and now U.S.Pat. No. 6,941,508; which is a divisional of U.S. application Ser. No.09/399,777 filed Sep. 21, 1999 and now U.S. Pat. No. 6,654,933; which isa continuing application of U.S. patent application Ser. No. 08/829,283,filed Mar. 31, 1997, now U.S. Pat. No. 5,973,679 which issued Oct. 26,1999; each of which applications are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to media delivery systems. Moreparticularly, the present invention relates to a system and method forimplementing interactive media delivery. Still more particularly, thepresent invention relates to a system and method for media streamindexing and synchronization.

2. Related Art

Recent advances in data handling and data communications techniques haveenabled the entertainment industry to provide movies and other audio,video, or multi-media program materials to viewers in a viewer's home ata time requested by the viewer. Such services are referred to as“video-on-demand” (VOD) services. Video-on-demand services allow aviewer to request and receive program materials at the viewer'stelevision set at a time specified by the viewer.

However, conventional video-on-demand services have limited ability orflexibility to customize program materials transmitted to the viewer.Typically, program materials are stored in a format such that theycannot easily be edited, modified, or packaged in a customized manner bythe video-on-demand service provider. Because of this limitedflexibility, the VOD service provider has a limited range or variety ofproducts that can be offered to the viewer.

This limited flexibility often results in a less than optimal mix ofprogram material being transmitted to the viewer, with less than optimaluse of available bandwidth. For example, a VOD service provider may beunable to provide additional program material desired by a particularviewer, such as closed-captioning text. Alternatively, the VOD serviceprovider may be unable to modify program material transmitted to theviewer to better suit the needs of the viewer, such as transmitting theaudio program material in an alternative language. Finally, the VODservice provider may be wasting bandwidth by transmitting programmaterial, such as closed-captioning text, that a particular viewer maynot be using.

In addition, conventional video-on-demand services do not offerinteractive capabilities to the viewer. Once the viewer orders aprogram, the program is delivered (e.g., transmitted) to the viewer'stelevision set for display at the specified time. The viewer has nocontrol over the program material while it is airing. For instance, theviewer cannot pause, fast-forward or rewind the program. All the viewercan do is watch the program as it is delivered, and, as such, theconventional video-on-demand system is not interactive.

SUMMARY OF THE INVENTION

The present invention is directed to a hierarchical structure used forstorage and delivery of program materials such as video and other media.In this document, the terms “program”, “program material”, and “programcontent” are used generally to refer to media provided to a viewer, suchas audio, video, multi-media, or other types of material intended forlistening and/or viewing by the viewer.

According to the invention, a hierarchy of object types is used toformat or arrange the program material that is transmitted to anindividual viewer. The objects include: an atom; a segment; a series;and a group. An atom contains the program material in the form of data,preferably encoded data, that is stored on a storage device or othermemory means. The object hierarchy of the present invention is generallydefined as follows: a group is comprised of one or more series; a seriesis comprised of one or more segments; and a segment identifies orreferences a portion of an atom, such as the data contained in an atomthat occurs between two points in time. As such, a segment may identifyall or part of an atom.

In one embodiment of the present invention, a method is provided forlocating program material so that delivery of the program material to aviewer begins at a specified time T in the program material. Thisindexing method of the present invention includes accessing a grouphaving one or more series, each series having one or more segments thatreferences a corresponding atom containing media data representing theprogram material.

This indexing method further includes steps for determining the dataposition of the program material corresponding to the specified time T.One step is dining in which segment the specified time occurs; thissegment is referred to as the specified segment, and the correspondingatom is referred to as the specified atom. The specified time T isconverted to specified-segment relative time T_(seg). In a preferredembodiment, this is done by calculating the elapsed time into thespecified segment at which the specified time occurs. T_(seg) isconverted to a data position relative to the specified atom, therebylocating media data representing the pram material at the specified timeT.

In a preferred embodiment, T_(seg) is converted to specified-atomrelative time T_(atom). In a particularly preferred embodiment, this isdone by adding the specified-segment's offset to T_(seg). An indexnumber is computed from T_(atom) using an index duration. In a preferredembodiment, the index duration is the duration of a frame of media data.

In a preferred embodiment, the index number is used to identify a dataposition for the media data representing the program material at thespecified time T. In a particularly preferred embodiment, an index fileis used to correlate index number with a corresponding data position. Inparticularly preferred embodiments, the corresponding data positions arethe beginning of a frame of media data, or the beginning of a group ofpictures of media data.

In a further embodiment of the present invention, a method is providedfor synchronizing media data for delivery to a viewer. Thesynchronization method of the present invention includes identifying abase atom containing media data, and identifying one or more auxiliaryatoms containing media data to be synchronized with the media data inthe base atom. This synchronization method further includes constructinga base atom index file that contains base atom index boundaries. In apreferred embodiment, the base atom index boundaries are Groups ofPictures boundaries.

This synchronization method also includes constructing an auxiliary atomindex file for each of the auxiliary atoms. Each auxiliary atom indexfile is constructed by selecting the auxiliary atom index boundariesthat most closely match the base atom index boundaries, therebysynchronizing media data in the auxiliary atoms with media data in thebase atom.

In further embodiments of the present invention, apparatus is providedfor implementation of the foregoing indexing and synchronizationmethods.

In yet further embodiments of the present invention, computer programproducts for use with a computer system are provided. One such computerprogram product includes a computer usable medium having computerreadable program code for enabling a computer system to carry out theindexing method of the present invention. Another such computer programproduct includes a computer usable medium having computer readableprogram code for enabling a computer system to carry out thesynchronization method of the present invention.

In yet a further embodiment of the present invention, a system isprovided for interactive delivery of program material to a viewer. Asused herein, a viewer can be a television viewer, a user of aworkstation, or any other entity that receives the program material.This system includes formatting means for arranging media datarepresenting program material in accordance with a viewer command fromthe viewer, the media data being arranged using the object hierarchy ofthe present invention. This system also includes computer means in datacommunication with the formatting means. The computer means isconfigured to receive the viewer command from the viewer, to transmitthe viewer command to the formatting means, and to receive the formattedprogram material from the formatting means for display to the viewer.

FEATURES AND ADVANTAGES

One feature of the present invention is that it is extensible.Additional atoms can be stored, and new segments, series, and groupscreated. Additional segments can be added to existing series, andadditional series can be added to existing groups.

Another feature of the present invention is that it is flexible. Mediadata can be arranged in an infinite variety of ways for delivery to aviewer without changing the object hierarchy, or modifying the mediadata contained in the atoms. Program material data can be partitionedinto atoms in numerous ways, only one of which is by media type (e.g.,video data in one atom and audio data in another atom).

A further feature of the present invention is that it is adaptable. Theobject hierarchy can be used with various encoding or data compressionprotocols. For example, with an MPEG-1 encoding protocol, audio data andvideo data can be encoded and contained in different atoms. With anMPEG-2 encoding protocol, the audio and video data can be contained in asingle atom.

An advantage of the present invention is that many different types ofsources of atom data can be used. Data sources may include disk files,shared memory, or even live data sources, such as with audio or videoconferencing. A further advantage of the present invention is that itoptimizes media delivery from the view point of a viewer and a mediaprovider. A viewer has interactive control over the content of theprogram material. An optimal mix of program material is transmitted tothe viewer, with optimal use of system bandwidth and memory.

The present invention has the further advantage of full interactivecontrol by the viewer over the program material received. The viewer cancontrol not only the content, but the mode in which it is viewed.

Further features and advantages of the present invention, as well as thestructure and operation of various embodiments of the present invention,are described in detail below with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the accompanyingdrawings. In the drawings, like reference numbers indicate identical orfunctionally similar elements. Additionally, the left-most digit(s) of areference number identifies the drawing in which the reference numberfirst appears.

FIG. 1 shows the relationship between a segment and its correspondingatom, with time advancing to the right as shown by the arrow in thefigure;

FIG. 2 shows the relationship between a group, two series within thegroup, and multiple segments within each of the two series;

FIG. 3 shows one embodiment of a group that includes two series, eachseries containing one segment, and each segment referencing the entiretyof its corresponding atom;

FIG. 4 shows a further embodiment of a group that includes two series,each series containing multiple segments, illustrating interleaving ofvaried program materials from a plurality of atoms to form a composite;

FIG. 5 shows an embodiment of a group that interleaves three series,each series containing a plurality of segments, illustrating the specialeffect capability of the object hierarchy of the present invention;

FIG. 6 shows a computer system suitable for storing and arranging mediadata for delivery to a viewer using the object hierarchy of the presentinvention and suitable for implementing the indexing and synchronizationmethods of the present invention;

FIG. 7 shows a flow diagram illustrating a process for determining thelocation of media data corresponding to a specified point in time in anitem of program material;

FIG. 8 shows an example of determining, in accordance with the processof FIG. 7, a byte position in an atom corresponding to a time T_(movie)in a movie;

FIG. 9 shows the relationship between frames and groups of pictures inMPEG-1 encoded video data, and shows an example of the indexing andsynchronization methods of the present invention using MPEG-1 encodedvideo and MPEG-1 encoded audio data;

FIG. 10 shows a flow diagram illustrating a process for synchronizingone or more auxiliary atoms containing media data with a base atomcontaining media data;

FIG. 11 shows a block diagram of a media delivery system that uses theobject hierarchy and indexing and synchronization methods of the presentinvention for interactive delivery of program material to a televisionviewer; and

FIG. 12 shows a block diagram of a media delivery system that uses theobject hierarchy and indexing and synchronization methods of the presentinvention for interactive delivery of program material to a workstation.

DETAILED DESCRIPTION OF THE EMBODIMENTS

1. Overview

The present invention is directed to a system and method forimplementing interactive media delivery to enable a viewer to haveinteractive control over program material delivered to the viewer. Forexample, a media provider may transmit program material over a networkto a set-top box so that the program material may be played on theviewer's television. Examples of program material include withoutlimitation movies, shows, concerts, how-to and instructional videos,live video and audio, home shopping programs, video games, sportingevents, news, and music.

In one scenario, a media provider obtains the program material to bedelivered to the viewer from a content provider. For example, a mediaprovider may obtain a movie from a content provider in the form of atape or reel that contains audio and video tracks for that movie.Alternatively, a content provider may deliver to a media provider a livedata feed that contains the audio and video from a live concert or livecoverage of a news event.

The program material is usually encoded or transformed into data by thecontent provider and then provided to the media provider. Alternatively,the media provider could encode the program material provided by thecontent provider. For example, audio and video tracks of the programmaterial may be encoded by such encoding or data compression protocolsas MPEG-1 (ISO/IEC 11172, “Information Technology—Coding of movingPictures and Associated Audio for Digital Storage Media at up to about1.5 Mbit/S”) or MPEG-2 (ISO/IEC 13818, “Information Technology—GenericCoding of Moving Pictures and Associated Audio”), and provided to themedia provider. The term “MPEG” refers to the Moving Picture ExpertsGroup. The encoded data may then be stored in a storage device or othersuitable memory means from which it can be accessed immediately, or at alater time. For example, the audio and video tracks of a movie may beencoded and stored in a file on a file server, or, alternatively, storedin a region of a shared memory device. The program material, a movie forexample, has now been transformed into data and stored for futureaccess. In accordance with the object hierarchy of the presentinvention, the program material data is stored as an atom of the presentinvention. For example, an atom of the present invention may containvideo data, audio data, or both video and audio data.

The object hierarchy of the present invention allows program material tobe provided to the viewer in an interactive and customized mannerwithout changing or modifying the atom, i.e., without changing ormodifying the program material data. The object hierarchy of the presentinvention allows program material to be transmitted to a viewer in amanner selected by the viewer, and in different ways to differentviewers, without changing or modifying the program material itself. Thesame program material can be arranged or formatted in different ways fordelivery to different viewers without having to alter or duplicate theprogram material. For example, the video for a movie can be packagedwith English language audio and transmitted to one viewer. The video forthat same movie can be packaged with Spanish language audio and Englishlanguage closed-captioning text and transmitted to another viewerwithout having to modify the video data, or duplicate the video data ina separate file.

2. Object Hierarchy

In order to provide flexibility in media delivery, as well asinteractive control by a viewer, an object hierarchy was developed thatallows accessing and arranging data in an infinite variety of ways. Theobject hierarchy of the present invention provides for sequentiallyordering data (concatenating in an ordered sequence) for transmissionserially in time, and grouping data in a parallel manner fortransmission simultaneously. The parallel data may be transmitted in asynchronized or an a synchronized manner.

As described generally above, the data representing the program materialis contained in an atom. The data representing any particular item ofprogram material can be divided or partitioned into several differentatoms. As one example, a movie can be partitioned into two atoms, oneatom for video, and another atom for audio. As a further example, themovie can additionally include a third atom containing closed-captioningtext. In still a further example, both audio and video data for a moviecan be contained in a single atom. As these examples illustrate, for anyparticular item of program material, there are numerous ways in whichthe data can be partitioned into atoms. Such partitioning may include,but is not limited to, partitioning by media, e.g., video in one atomand audio in another atom.

An atom may be stored in any suitable manner on a storage device orother suitable memory means. This may include, for example, a file on adisk in a server, an area of a shared memory region, or a memory suchrain memory 608 or a secondary memory 610 (discussed in more detailbelow in connection with FIG. 6). An atom is assigned a unique atomidentifier, or atom ID, when the atom is stored. Each atom includesinformation describing the atom. For example, information in the atommay include one or more of the following: the atom ID; an atom length(program material data length or temporal length or duration of theprogram material); a data type (e.g., video, audio, ASCII); a datasource (storage location of the program material data itself, e.g., aUNIX file, identification of a memory region, or a live data feed); anindex source (a file or region that contains various indices, such asfor locating data points and synchronizing data); an index duration(time between indexed points); and an encoding protocol (if any) used totransform the program material into data for storage. An atom may alsofurther include a set of allowable playback modes that indicate thesuitability of the atom data for reverse or fast-forward play.

An atom is thus the basic building block of the object hierarchy of thepresent invention. An atom describes the program material data, andidentifies the storage location of the actual program material data. Inthat sense, an atom will be referred to in this document as “containing”the actual program material data. Program material data contained in anatom is accessed, and arranged or formatted for delivery to a viewerthrough the object hierarchy of the present invention.

A segment identifies a portion of one particular atom, i.e., programmaterial data or “atom data” between two points in time. A segment mayidentify the entire atom, i.e., atom data between the beginning andending times of the program material. Alternatively, a segment mayidentify only a portion of the atom, for example, atom data between thebeginning of the program material and another arbitrary time in theprogram material, atom data between an arbitrary time in the programmaterial and the end of the program material, or atom data between twoarbitrary times in the program material.

Each segment is assigned a unique segment identifier or segment ID whenit is stored. In a preferred embodiment of the present invention, eachsegment is defined by an atom ID, an offset (time between the beginningof the atom and the beginning of the segment), and a duration (timebetween the beginning of the segment and the end of the segment). Asegment that corresponds to an entire atom would have an offset of zero,and a duration equal to the duration of the atom.

FIG. 1 illustrates the relationship between an atom and a segment.Referring now to FIG. 1, an atom 104 is shown that contains data forprogram material. Segment 108 identifies a portion of atom 104. Segment108 extends from time t₁ to time t₂, and identifies the data in atom 104between corresponding data locations D₁ and D₂. Segment 108 is definedusing the parameters of offset 132 and duration 134. Offset 132 isdefined as the time between the beginning of the atom (t₀) and thebeginning of segment 108 (t₁). Duration 134 is defined as the timebetween t₁ and t₂, or the temporal length of segment 108. In theembodiment illustrated in FIG. 1, offset 132 and duration 134 arespecified in units of time, as shown by the arrow at the bottom of thefigure indicating time progressing to the right. Alternatively, offset132 and duration 134 may be specified in units of data length, such asbytes.

Segment 108 may begin contemporaneously with the beginning of atom 104at time t₀. In that situation, offset 132 is equal to zero. With offset132 equal to zero, duration 134 of segment 108 may be equal to theduration of atom 104. In the latter situation, segment 108 representsthe entirety of atom 104 (see also FIG. 3).

A series is formed by sequentially ordering one or more segments. Aseries is a set of one or more segments that are joined or concatenatedfor sequential delivery of the corresponding data. A series can bedescribed in one embodiment as an ordered list of segments. A series isassigned a unique series identifier or series ID when it is stored. Inan alternative embodiment, a series can be described as an ordered listof segment IDs. The length of a series is the sum of the length of itscomponent segments.

A group is formed by joining or grouping series in parallel forparallel, simultaneous delivery of the corresponding data. Preferably,the delivery of the series in a group is synchronized. This is usefulwhere one series is a set of segments identifying a video atom, and theother series is a set of segments identifying the corresponding audioatom. Such synchronized delivery enables the video to be synchronizedwith the audio. A group is assigned a unique group identifier or groupID when it is stored. In one embodiment, a group can be described as aparallel arrangement of series IDS.

In the object hierarchy of the present invention, a series mayalternatively be defined as an empty set of zero segments. Similarly, agroup may alternatively be defined as an empty set of zero series.However, such groups and series will not be useful for identifying andformatting program material data. As such, the invention will bedescribed herein with respect to a group having at least one (one ormore) series, and a series having at least one (one or more) segment.

FIG. 2 is a diagram illustrating two series 208 (208A and 208V) and agroup 218. Referring now to FIG. 2, each series comprises a sequence ofsegments 108. In the example illustrated in FIG. 2, series 208A iscomprised of segments 108A1, 108A2, 108A3, etc. Series 208A lists orjoins segments 108A1, 108A2, 108A3, etc. in the correct sequentialorder. Similarly, series 208V lists or joins segments 108V1, 108V2,108V3, etc. in the correct sequential order. The example illustrated inFIG. 2 further shows that group 218 is comprised of two series: series208A; and series 208V.

In an example where the program material is a movie, series 208A may bea series of segments 108 corresponding to audio data in one or moreaudio data atoms 104 (not shown). Likewise, series 208V may be a seriesof segments 108 corresponding to video data in one or more video dataatoms 104 (not shown). In such an example, group 218 is the paralleloccurrence (delivery, playback, etc.) of the audio and video portions(series 208A and 208V, respectively) of the movie. As can be seen fromFIG. 4, segments in a series can point to the same or different atoms.

A media delivery system using the object hierarchy of the presentinvention delivers program material to a viewer as defined by a group. Agroup serves as the “formula” for arranging the program material to bedelivered to a viewer. A media delivery system using the objecthierarchy of the present invention has a high degree of flexibility. Afew examples of this flexibility include, without limitation, theability to provide delivery options such as language choices for audioand closed-captioning text, and the ability to provide customizedprogram material with special effects and alternative media insertion.

Three examples will now be describe to illustrate the flexibilityprovided by the object hierarchy of the present invention. The firstexample illustrates the delivery of program material to a viewer withoutmodification. The second example illustrates inserting or interleavingone type of program material (such as a commercial) into another type ofprogram material (such as a movie). The third example illustrates how aplurality of different types of program material can be arranged toprovide custom program material formatting and special effects.

FIG. 3 is a diagram illustrating the first example where programmaterial is delivered to a viewer without modification. In this example,the viewer is delivered a group 218 that includes two series 208A and208V. Series 208A and 208V each contain a single segment 108A and 108V,respectively. Segment 108A corresponds to the entirety of atom 104A, andsegment 108V corresponds to the entirety of atom 104V. Offset 132 ofeach segment 108A and 108V is zero, and duration 134 is equal to theduration of atom 104A and 104V, respectively.

In the example shown in FIG. 3, atom 104A may contain audio data for amovie, and atom 104V may contain the corresponding video data for themovie. A viewer watching this movie would see video and hear audiotogether. Alternatively, atom 104A may contain audio and video data foran instructional how-to program, and atom 104V may contain instructionaltext for the how-to program. A viewer watching such a how-to programwould see video and instructional text, as well as hear audio togetherwith the video and text.

FIG. 4 is a diagram illustrating the second example referred to abovewhere varied program materials are interleaved to form a compositeprogram material that is delivered to a viewer. As in the previousexample illustrated in FIG. 3, a viewer is delivered a group 218 thatincludes two series 208A and 208V. However, in the example shown in FIG.4, each series 208A and 208V is made up of a plurality of segments 108.As illustrated in FIG. 4, series 208A includes 16 segments (108A1through 108A16) and series 208V also includes 16 segments (108V1 through108V16). Only selected segments have been labeled for clarity. It is tobe understood that 16 segments in each series have been shown forillustrative purposes only, and that the number of segments in eachseries can vary, and is not limited to 16.

Segments 108 shown in FIG. 4 correspond to portions of four differentatoms 104A, 104V, 104CA, and 104CV. Particularly, segments 108 of series208A correspond to portions of atoms 104A and 104CA, while segments 108of series 208V correspond to portions of atoms 104V and 104CV. Thecorrespondence between series 208A and the atoms has been omitted forclarity, but would be analogous to that shown for series 208V.

The embodiment illustrated in FIG. 4 will be described in terms of anexemplary embodiment where the program material ordered by a viewer is amovie, and the media provider wishes to include commercials inserted atintervals during the movie. In such an exemplary embodiment, the movieis partitioned into atom 104A for audio, and atom 104V for video. In theexemplary embodiment, a second type of program material to beinterleaved within the movie is a set of three commercials. In thisexample, the commercials are all partitioned into two atoms, 104CA thatcontains the audio for all of the commercials, and 104CV that containsthe video for all of the commercials. Alternatively, each of the threecommercials could be partitioned into its own pair of atoms (e.g., onefor audio and one for video). In a further alternative, each of thethree commercials could be contained in a single atom (audio and videocombined in one atom for each commercial). Although the foregoing andother alternatives may be preferred, the following discussion refers tothe partitioning shown in FIG. 4.

To insert the set of three commercials into the movie, segmentscorresponding to commercial atoms 104CV and 104CA are interleavedbetween segments corresponding to movie atoms 104V and 104A,respectively, as illustrated in FIG. 4. Particularly, segments 108V2,108V3, and 108V4, corresponding to the video portion CV1, CV2, and CV3of the first set of three comments in atom 104CV, are inserted betweensegments 108V1 and 108V5, corresponding to the video portion MV1 and MV2of the first two parts of the movie in atom 104V. Similarly, segments108V6, 108V7, and 108V8, corresponding to the video portion CV4, CV5,and CV6 of the next set of three commercials in atom 104CV, are insertedbetween segments 108V5 and 108V9, corresponding to the video portion MV2and MV3 of the next two parts of the movie in atom 104V.

A viewer watching the program material delivered in accordance withgroup 218 as illustrated in FIG. 4 sequentially sees a portion of themovie (video portion MV1 together with audio portion MA1), followed by aset of three commercials (video portions CV1, CV2, and CV3 together withaudio portions CA1, CA2, and CA3), followed by the second portion of themovie (video portion MV2 together with audio portion MA2), followed by asecond set of three commercials (video portions CV4, CV5, and CV6together with audio portions CA4, CA5, and CA6), and so on until the endof the program material identified by group 218.

In the exemplary embodiment of FIG. 4, segments 108A1-108A16 have thesame offset 132 and duration 134 as their counterpart segments108V1-108V16. As illustrated in FIG. 4, segments 108A1 and 108V1 have anoffset 132 of zero and a duration 134 of t₁−t₀. In the preferredembodiment of the present invention, program material begins at timet₀=0. Thus, duration 134 of t₁−t₀=t₁. Similarly, segments 108A2 and108V2 have an offset from the beginning of series 208A and 208V,respectively, of t₁. Segments 108A2 and 108V2 have an offset 132 of zerobecause each segment corresponds to the beginning of atom 104CA and104CV, respectively. Segments 108A2 and 108V2 have a duration 134 oft₂−t₁.

As a further illustration, segments 108A5 and 108V5 have an offset 132of t₁ measured from the beginning of corresponding atoms 104A and 104V,respectively. As shown in FIG. 4, portion MV2 of atom 104V thatcorresponds to segment 108V5, and portion MA2 of atom 104A thatcorresponds to segment 108A5, begin at time t₁. Segments 108A5 and 108V5have a duration 134 of t₅−t₄. Similarly, segments 108A13 and 108V13 havean offset 132 of t₁+(t₅−t₄)+(t₆−t₅) that corresponds to the beginning ofMA4 and MV4, respectively. Duration 134 of segments 108A13 and 108V13 ist₁₃−t₁₂. As yet a further illustration, segments 108A7 and 108V7 have anoffset 132 of (t₄−t₁)+(t₆−t₅) that corresponds to the beginning of CA5and CV5, respectively. Duration 134 of segments 108A7 and 108V7 ist₇−t₆. A similar analysis is used to determine offset 132 and duration134 for the remaining segments in group 218.

Other examples of the embodiment illustrated in FIG. 4 are alsocontemplated. One such example is for an instructional program. In suchan example, atoms 104V and 104A are the video and audio, respectively,of the instructional portion of the program material, while atoms 104CVand 104CA are the video and audio, respectively, for questionspertaining to the instructional portion of the program material.

In yet another example of the embodiment illustrated in FIG. 4, theprogram material is again a movie. However, instead of interleavingcommercials during the movie, movie previews of other movies areinserted. In such an example, segments 108 corresponding to atoms 104CVand 104CA are the video and audio portions, respectively, of the moviepreviews to be inserted during presentation of the movie contained inatoms 104V and 104A. Alternatively, the movie-preview program materialcould be inserted at either the beginning or the end of the movie, aswell as in the middle, to entice the viewer to order further movies.

FIG. 5 illustrates a third example wherein a plurality of differentseries 208 are arranged to provide custom program material formatting,and to use the object hierarchy to produce special effects as explainedbelow. According to the illustrated embodiment, group 218 includes threeseries 5081, 5082, and 5083. Series 5081 includes two video segments108V1 and 108V3, a null segment 108N2, and an audio segment 108A4.Series 5082 has a null segment 108N1, and a video segment 108V2. Series5083 has four audio segments 108A1, 108A2, 108A3, and 108A5, and onevideo segment 108V4. The atoms corresponding to each of the foregoingsegments have been omitted for clarity.

In delivering group 218 illustrated in FIG. 5 to a viewer, series 5081,5082, and 5083 may be transmitted in a parallel, synchronized manner. Insuch a transmission, video segment 108V1 is delivered contemporaneouslywith audio segment 108A1. During this time interval, null segment 108N1functions as a space or time marker for series S082, during which timeno data is transmitted to the viewer from series 5082. Prior to the endof delivery of video segment 108V1, delivery of video segment 108V2 fromseries 5082 begins. The phaseout of video segment 108V1 and phase in ofvideo segment 108V2 can be accomplished using any of a number oftechniques known in the art, such as a “wipe”, a “dissolve”, or othertype of “special effect”. During the phaseover from video segment 108V1to video segment 108V2, the audio portion of the program materialchanges from audio segment 108A1 to audio segment 108A2. Null segment108N2 is used to mark time in series 5081 between video segments 108V1and 108V3. After null segment 108N2 is completed, the video portion ofthe program material begins to phaseover from video segment 108V2 tovideo segment 108V3. During the phaseover period, the audio portionchanges from audio segment 108A2 to audio segment 108A3 in series 5083.Audio segment 108A4 is delivered with video segment 108V4. The programmaterial ends with audio segment 108A5 delivered without accompanyingvideo.

The embodiment shown in FIG. 5 is particularly illustrative of howvarious segments can be arranged in series, and the series in groups,thereby providing tremendous flexibility in the delivery of media to aviewer. For example, null segments can be used to skew or offset thedelivery of data from one atom with respect to data from another atom.

Note that the foregoing examples have been described in terms of audioand video portions of the program material being stored in separateatoms 104. However, the object hierarchy of the present invention is notlimited to such partitioning by media. For example, an atom 104 cancontain both the audio and the video for an item of program material.Alternatively, an atom can contain graphics for a game, with a secondatom containing sound effects for that game, and a third atom containingan instructional text overlay for the game graphics. In this manner, aviewer or game player could select whether they wanted to receivedelivery of the sound effects or the instructional text, i.e., the soundeffects and the instructional text could be turned on and off under thecontrol of the game player. In yet a further alternative, the graphics,sound effects, and instructional text can all be contained in a singleatom.

In yet another alternative embodiment, consider program material that isavailable in multiple languages. In this embodiment, a viewer can selecta language from a menu of language choices. In that way, only the datafrom atom 104 containing the program material in the selected languageare delivered to the viewer, with or without accompanying video. In sucha scenario, the audio and video may be in separate atoms so that manyaudio atoms in different languages could accompany the same video atom.This has the benefit of saving on storage space. When video and audioare combined in one atom, each language would require an implicit copyof the video. However, when audio and video are stored separately, onecopy of the video can serve all of the audio languages. Additionally,new audio atoms can be added without affecting the video atom, orneeding to duplicate the video atom.

In yet another example, the object hierarchy of the present inventioncould be used in an audio or video conferencing environment, or otherenvironments where the source for the atom data is a live data feed.

The object hierarchy of the present invention may also be used tosynchronize delivery of program material to two or more differentviewers. Each series in a group could be delivered simultaneously to twoor more viewers, thereby having delivery to one viewer remainsynchronized with delivery to other viewers. For example, a lecturebeing given in one location can be delivered simultaneously to allaudience members, e.g., students. Each audience member could be in adifferent location, and in a location remote from the lecturer.

The object hierarchy of the present invention affords the media providergreat flexibility to offer a viewer a broad range of program materialproducts. As illustrated above with several examples, a media providercan deliver program materials in a format that suits the needs of themedia provider, as well as the desires of an individual viewer. Theobject hierarchy of the present invention also allows alternative formsof the same program material to be provided to various viewers withouthaving to store multiple and/or different versions of the same programmaterial. The media provider can use atoms of program material toarrange custom program content that is different for each delivery. Tocustomize program material for a viewer, it is not necessary to changeor modify data in the atoms of that program material. Rather, all thathas to be changed is the composition of the group delivered to theviewer.

The above examples are provided to help describe the media objecthierarchy provided according to the invention, as well as to illustratea few of the numerous possibilities available to a media provider forstoring, arranging, and transmitting program material, and to a viewerfor viewing program material. The examples and embodiments describedabove are provided by way of example only and should not be construed aslimitations.

In a further embodiment, the present invention is directed to a computersystem for storing and arranging media data for delivery to a viewerusing the object hierarchy as described herein. An exemplary computersystem 602 is shown in FIG. 6. Computer system 602 includes one or moreprocessors, such as processor 604. Processor 604 is connected to acommunication bus 606.

Computer system 602 also includes a main memory 608, preferably randomaccess memory (RAM), and a secondary memory 610. Secondary memory 610includes, for example, a hard disk drive 612 and/or a removable storagedrive 614, representing a floppy disk drive, a magnetic tape drive, acompact disk drive, etc. Removable storage drive 614 reads from and/orwrites to a removable storage unit 616 in a well known manner. Mainmemory 608 may be used to store atoms (including the program materialcontained therein), as well as other data such as index sources or datalocations, in accordance with the object hierarchy of the presentinvention. Alternatively, secondary memory 610 may be used to store atomdata and index sources.

Removable storage unit 616, also called a program storage device or acomputer program, product, represents a floppy disk, magnetic tape,compact disk, etc. As will be appreciated, removable storage unit 616includes a computer usable storage medium having stored therein computersoftware and/or data.

Computer system 602 is connected to a network 618 so that programmaterial may be retrieved and delivered to a viewer. Computer system 602may communicate via network 618 with other computer systems or servers.Computer system 602 may also communicate via network 618 with a mediadelivery system for delivery of program material to a television viewer,to a workstation, or to other recipients.

Computer programs (also called computer control logic) are stored inmain memory 608 and/or secondary memory 610. Such computer programs,when executed, enable computer system 602 to implement the objecthierarchy of the present invention. In particular, the computerprograms, when executed, enable processor 604 to store and arrange mediadata for delivery to a viewer using the object hierarchy of the presentinvention. Accordingly, such computer programs represent controllers ofcomputer system 602.

In another embodiment, the invention is directed to a computer programproduct comprising a computer readable medium having control logic(computer software) stored therein. The control logic, when executed byprocessor 604, causes computer system 602 to store, arrange, format, anddeliver media data to a viewer using the object hierarchy of theinvention as described herein.

In another embodiment, the invention is implemented primarily inhardware using, for example, a hardware state machine. Implementation ofthe hardware state machine to store and arrange data using the objecthierarchy of the present invention will be apparent to persons skilledin the relevant arts.

3. Media Stream Indexing

Conventional media delivery systems, such as conventionalvideo-on-demand systems, do not provide a way for a viewer to skip orjump to selected points in the program material. Conventional mediadelivery systems also do not allow the viewer to view the programmaterial in special modes such as slow motion, still, pause,single-frame advance, fast-forward, reverse, etc. Instead, withconventional systems, a viewer is forced to watch or view the programmaterial in conventional playback mode as it is being transmitted by themedia provider. The present invention provides a system and method forallowing a viewer to control delivery of the program material to jump orskip (either forward or backward) to selected points in the programmaterial. Additionally, the present invention allows a viewer to viewthe program material in any of the above-defined special modes, as wellas in a conventional playback mode.

In order to provide a viewer with interactive control for viewingprogram material in special modes, an indexing method was developed tocorrelate between time and program material data or atom data location.The indices used with the method of the present invention wouldtypically be generated by a media provider. For example, to allow aviewer to skip to a certain time in the program material, the viewerspecifies the particular time to which the viewer would like to skip. Inresponse, program material is delivered to the viewer by the mediaprovider beginning from the corresponding data position.

To view program material in special modes such as slow-motion, still,pause, etc., it is necessary to locate a particular time in the programmaterial, and to deliver program material data corresponding to thatparticular point in time. As discussed more fully below, in anenvironment in which program material is temporally divided into frames,it is necessary to locate the frame that corresponds to the particulartime, and to deliver one or more frames of program material databeginning with the corresponding frame.

FIG. 7 is a flow diagram illustrating a process for determining thelocation of media data corresponding to a particular or specified pointin time in the program material. In this document, the specified pointin time is referred to as an epoch. Referring now to FIG. 7, in a step704, a request is received to deliver the program material from aspecified point in time (the epoch). For example, a viewer may requestthat the program material skip to a specific time, or a viewer mayrequest that delivery advance to a certain milestone in the programmaterial, such as the beginning of the next act of a play.

In a step 708, it is first determined in which segment the epoch occurs.For programs having a series that contains only one segment, the epochoccurs in that segment. For programs having a series that contains morethan one segment, the first step in the process is determining in whichsegment the epoch occurs.

In a step 712, a segment-relative time T_(seg) of the epoch isdetermined. Segment-relative time T_(seg) is the amount of time into thesegment at which the epoch occurs.

In a step 716, segment-relative time T_(seg) is converted into anatom-relative time T_(atom). Atom-relative time T_(atom) is the amountof time into the corresponding atom at which the epoch occurs.

In a step 720, atom-relative time T_(atom) is converted to an indexnumber IN by dividing T_(atom) by an index duration ID. Index durationID is preferably a constant, and is one of the attributes or informationitems stored in an atom. An index rate IR is the mathematical reciprocalor inverse of index duration ID so that IR=1/ID and ID=1/IR. Because ofthis reciprocal relationship, either the index rate or the indexduration can be used to compute index number. Index number INcorresponds or maps to a byte-relative position of the epoch in thecorresponding atom.

If an epoch selected by a viewer is in the middle of a frame or otherparsed data unit, it is necessary to “round down” to the beginning ofthat frame, or “round up” to the next flame. This is achieved byrounding index number IN in a step 722 to locate a frame boundary, orother index boundary. When the epoch is in the middle of a frame thatoccurs near or at the end of a segment, rounding up to the next framemay result in the epoch occurring in the next segment Similarly,rounding down may result in the epoch occurring in the previous segment.Although index number IN is preferably an integer value, a functionother than simple arithmetic rounding (e.g., a floor or ceilingfunction) may be required. For example, as explained more fully below,some byte positions may be repeated in an index source. In thatsituation, the step of rounding includes scanning the index source forthe next different byte position that corresponds to the beginning ofthe next Group of Pictures.

In a step 724, index number IN is used to determine byte position. Inone embodiment, an index source such as an index file is used to mapfrom index number IN to byte position. In such an embodiment, an indexfile may contain a sequence of 64-bit byte positions corresponding tothe index numbers. The index source contains the byte positions, andindex number IN is used to map to the byte position by identifying theoffset from the beginning of the index file at which that byte positionis located. Index numbers within an atom are unique, and are notrepeated.

An example will illustrate this process. Assume that it is necessary tolocate the byte position of data occurring one second (1 sec=10⁶ μsec)into an atom. Assume an index duration of approximately 1/30 sec (33,000μsec), the preferred index duration of video data. Index number IN maybe computed as follows:

${I\; N} = {\frac{10^{6}\mspace{11mu}{\mu sec}}{33\text{,}000\mspace{14mu}\mu\;\sec} = 30.}$Alternatively, index number IN may be computed by multiplying by theindex rate which is the reciprocal of the index duration:IN=10⁶ μsec×(3×10⁻⁵/μsec)=30.The byte position of data occurring at 1 second into the atom will belocated at index number 30 offset from the beginning of the index file.

In an alternate embodiment, an algorithm may be used in step 724 toconvert index number to byte position. Such an algorithm may, forexample, depend on actions previously taken, such as in aninteractive-plot movie. The present invention is not limited to the useof predetermined or precomputed indices. The present inventioncomprehends the use of indices that are determined or computed “on thefly” as they are needed.

Finally, in a step 728, program material data beginning at thebyte-relative position determined in step 724 is delivered to theviewer.

Process steps 708 through 728 of FIG. 7 are preferably carried out foreach series in a group. An implicit first step not shown in FIG. 7 isthe conversion from movie-relative time to series-relative timeT_(series). In a preferred embodiment of the present invention,movie-relative time is the same as series-relative time T_(series), withall series and movies (or other program material) beginning at timezero. Although this embodiment is preferred, the present invention isnot so limited, and there may be a time offset between programmaterial-relative time and series-relative time T_(series).

To further illustrate the process of FIG. 7, an example is provided inFIG. 8. In the example of FIG. 8, a viewer is watching a movie thatcomprises a group 218. Group 218 includes two series 208. Each series208 includes four segments 108. In accordance with the object hierarchydescribed above, each segment 108 corresponds to a part or all of anatom 104, and is defined by an offset 132 and a duration 134 withrespect to that corresponding atom. In this example, the viewer desiresto skip to a particular time in the movie, labeled as T_(movie) in FIG.8.

The process of converting from “movie-relative time” (T_(movie) in FIG.8) to “atom-relative byte position” will now be described with referenceto the process of FIG. 7. It is to be understood that the process iscarried out for each of series 208 of group 218 shown in FIG. 8. Inaccordance with step 708, it is determined that T_(movie) occurs in thesecond segment of each series, the duration of this segment being t₂−t₁.As described by step 712, T_(movie) is converted to segment relativetime T_(seg), where T_(seg) represents the elapsed time into the segmentat which T_(movie) occurs (T_(movie)−t₁).

In accordance with step 716, T_(seg) is then converted to atom-relativetime T_(atom). Atom 104 corresponding to the second segment is shown inFIG. 8. Offset 132 of the second segment is added to T_(seg) to obtainatom-relative time T_(atom).

The next step in the conversion process is determining the index numberin order to map T_(atom) to an atom-relative byte position. Inaccordance with step 720, index number IN is calculated by dividingT_(atom) by an index duration ID. In the example of FIG. 8, group 218represents a movie. For the purpose of this example, one of the seriesin group 218 may correspond to video data and the other may correspondto audio data. A preferred index duration ID for video data is theduration of a frame, typically approximately 1/30 sec. To convert to anindex number, T_(atom) is divided by an index duration equal toapproximately 1/30 see. It should be noted that in the preferredembodiment of the present invention, all times are calculated in unitsof microseconds.

If T_(movie) corresponds to a time that occurs in the middle of a frame,then index number IN is rounded to locate an index boundarycorresponding to a frame boundary, in accordance with step 722. Afterrounding, index number IN is used to determine byte position P inaccordance with step 724. For example, an index source or index file804, such as in the form of a lookup table, may be used to map orcorrelate index number IN to byte position P within the stored moviedata. Movie data will then be delivered to the viewer beginning at byteposition P, in accordance with step 728.

As noted above, group 218 in FIG. 8 includes two series. The process ofFIG. 7 as described above is preferably performed for each series.Generally, the index rate (or duration) used for a segment in one seriesin a group will not be the same as the index rate (or duration) used fora corresponding segment in another series in that group. For example,one of series 208 illustrated in FIG. 8 may correspond to video data,and the other series in grow 218 may correspond to audio data. As notedabove, a preferred index duration for video data is the frame duration,typically approximately 1/30 sec. A preferred frame duration for audiodata is 24 msec (approximately 1/42 sec corresponding to a frame rate of42/sec). However, a preferred index duration for audio data is to havethe same value as the preferred index duration for video data. Byselecting the same index duration for audio and video data, bettersynchronization between audio and video data can be achieved. However,the present invention is not limited to the use of the same index ratesor index durations for audio and video data.

The indexing method of the present invention allows a viewer to skip toan arbitrary point in time in an item of program material. Without anindex file to convert from program material-relative time toatom-relative byte position, program material data in an atom could onlybe accessed sequentially from the beginning to the end. It would not bepossible to jump or skip to an arbitrary time point in the programmaterial because the location of the program material data correspondingto that arbitrary time point would not be known.

Some program material is divided into frames, or other types of parseddata units. For example, video data is typically parsed by frames, eachframe having a fixed duration but varying in size. In an environment inwhich the program material is not divided into frames, the indexingmethod of the present invention provides a mapping between atom-relativetime T_(atom) and atom-relative byte position P to allow access to anarbitrary byte position.

However, in an environment in which the program material data is dividedor parsed into frames through encoding or otherwise, it is preferablethat the point to which a viewer skips or jumps is not completelyarbitrary. Specifically, it is preferred that the point to which theviewer skips is the beginning of a frame. For example, program materialmay be transmitted to a set-top computer where it is decoded for viewingon the viewer's television set. The decoder in the set-top boxrecognizes a “frame” of video data as a defined bit stream having astart code and an end code. If data transmitted to the set-top boxbegins in the middle of the frame, i.e., in the middle of the definedbit stream, it will not be recognized by the decoder, and will not bedisplayed to the viewer.

Where MPEG encoding is used, frames vary in size or amount of data(e.g., the number of bytes), but are always presented for the sameduration, typically approximately 1/30 sec. The data compression of MPEGencoding preserves the natural frame rate for video data of 30 framesper second. Although frames of data are delivered at a constant rate,the size or amount of data in each frame varies, so it is necessary todetermine the byte location of the beginning of any particular frame.The indexing method of the present invention allows program material tobe delivered from the beginning of a frame, rather than from anarbitrary byte position within a frame.

To ensure that, when converting from movie-relative time (time relativeto the program material) to atom-relative byte position, the byteposition corresponds to the beginning of a frame, an index file isconstructed for the atom containing the frame-partitioned data. Thisindex file includes byte offsets so that the atom-relative byte positionin the index file corresponds to “safe” frame, or other type of index,boundaries. The index file is constructed by processing the encoded datawith a tool that parses the encoded data in a manner suitable for theparticular encoding scheme. An encoding-scheme-specific tool identifiesindex boundaries suitable for that encoding scheme. In a preferredembodiment, one tool is used to construct index files for MPEG-1 encodedvideo data, another tool is used to construct index files for MPEG-1encoded audio data, and yet another tool is used to construct indexfiles for MPEG-2 encoded audio and video data.

An index source, of which an index file is one example, corresponds tothe atom from whose data it was generated. An index source is preferablygenerated one time, when the corresponding atom is encoded and/orinstalled on a media provider's delivery system. An index source ispreferably not generated each time the atom is used or delivered inorder to preclude having to parse encoded data repeatedly and “on thefly.” However, if the program material is “interactive” so that theprogram material delivered depends upon actions previously taken, suchas in an interactive-plot movie, then the index source is generated “onthe fly” as the atom is being used.

The program material can be delivered in the mode specified by a viewerby delivering the frames corresponding to the viewer's request. Forexample, for fast forward playback, frames can be delivered at a fasterrate, or periodic frames (i.e., every other or every third frame, etc.)can be skipped. For reverse playback, the frames can be delivered inreverse order. For jumping to a specified point in the program material,delivery begins at the frame corresponding to that point.

In some encoding protocols, such as MPEG-1, video data frames aregrouped together into units referred to herein as “Groups of Pictures”(GOPs). A GOP is comprised of one or more frames. In an environmentusing GOP, an index file is preferably constructed that allows a viewerto skip only to the beginning of a GOP, not simply to the beginning of aframe within the GOP. FIG. 9 illustrates the relationship between framesand a GOP. FIG. 9 shows MPEG-1 video data divided into twelve frames,shown as F1, F2, . . . F12. The twelve frames are further grouped intofour GOPs, shown as GOP1, GOP2, GOP3, and GOP4. Particularly, frames F1,F2, F3, and F4 are in GOP1, frames F5, F6, and F7 are in GOF2, framesF8, F9, F10, and F11 are in GOP3, and frame F12 is in GOP4. The timeaxis shown in FIG. 9 is marked at regular intervals, i.e., the frameduration or time for which a particular flame is presented, generallyapproximately 1/30 sec. Dashed lines correlate the beginning of eachframe with the corresponding time. Frame F1 begins at time t₁, frame F2begins at time t₂, frame F3 begins at time t₃, etc. The MPEG-1 videodata of FIG. 9 has a fixed index duration, the index duration being theduration of each frame, or 1/30 sec. FIG. 9 illustrates that althoughframes F1-F12 all have the same duration, the frames have varying sizes.For example, frame F1 is larger than frame F2, i.e., frame F1 containsmore data than flame 12.

MPEG-1 audio has only one grouping level so that “audio frames” are notfurther grouped into “audio GOPS”. The MPEG-1 audio data of FIG. 9 isbroken down into fifteen audio frames A1, A23, . . . A15. Each of theaudio frames shown in FIG. 9 has a fixed flame size so that there is thesame amount of data in each audio frame. The duration of each audioframe is the same. It can be seen from the time line in FIG. 9 that theindex duration for the audio data is the same as the index duration ofthe video data. Using equal index durations or equal index rates foraudio data and video data helps to correlate and synchronize the datawith each other. However, the present invention is not limited to theuse of equal index durations or rates for audio data and video data, andthe use of different index rates is contemplated for the presentinvention.

To ensure that program material data is delivered to a viewer beginningat the start of a GOP, and not just the start of a particular frame,each frame within a GOP maps to the atom-relative byte position of thebeginning of that GOP, which is also the beginning of the first frame inthat GOP. In an embodiment where the index rate equals the frame rate,every frame within a GOP is assigned a unique index number. The value ofthe atom-relative byte position corresponding to each of the indexnumbers of frames within a GOP will be the same, i.e., the atom-relativebyte position of the beginning of the first frame in the GOP. As anexample (not shown in FIG. 9), assume frames 30 through 40, inclusive,are in the same GOP. Assume further that the index rate is equal to theframe rate so that frames 30 through 40 map to index numbers 30 through40. The 64-bit byte positions for these eleven index numbers are thesame, and point to the beginning of frame 30. As another example, assumeindex numbers are determined only for every fifth frame. In such ascenario, the index rate is one-fifth the frame rate (and the indexduration is five times the frame duration). Again assume frames 30through 40 are in the same GOP. In this instance, there are indexnumbers for only frames 30, 35, and 40, and these are index numbers 6(30/5), 7 (35/5), and 8 (40/5), respectively. The 64-bit byte positionsfor these three index numbers are the same, and point to the beginningof frame 30.

Another example is illustrated in FIG. 9. Frames F1, F2, F3, and F4 inFIG. 9 are assigned unique index numbers, but each of these indexnumbers maps to the same atom-relative byte position that is thebeginning of GOP1, which is also the beginning of frame F1. Likewise,frames F8, A, F10, and F11 are assigned unique index numbers, but eachof these index numbers maps to the same atom-relative byte position thatis the beginning of GOP3, which is also the beginning of frame F8. Forthe MPEG-1 video data shown in FIG. 9, there are 12 unique indexnumbers, and 12 atom-relative byte positions made up of four sets: thefirst set contains four rated atom-relative byte positions for framesF1-F4; the second set contains three repeated atom-relative bytepositions for F5-F7; the third set contains four repeated atom-relativebyte positions F8-F11; and the fourth set contains one atom-relativebyte position for F12.

To locate the beginning of the next GOP in an index file, such as for“rounding up”, it is thus necessary to look for the next differentatom-relative byte position. Rounding down to the beginning of a GOP isaccomplished by the use of repeated atom-relative byte positions withinthe index source. The use of repeated atom-relative byte positions forthe frames within a GOP ensures that program material delivered to aviewer starts from the beginning of a GOP. In this example, the GOPrepresents the decodable data unit. The indexing method of the presentinvention allows program material to be delivered to a viewer from thebeginning of whatever decodable data unit is used.

The indexing method of the present invention correlates between time andmedia data location. Although the indexing method has been describedherein with respect to a particular object hierarchy (i.e., atoms,groups, series, and segments), the present invention is not limited to aparticular object hierarchy, or to any particular arrangement of mediadata. It is to be understood that the indexing method of the presentinvention can be used in conjunction with other methods of arrangingprogram material as media data.

For example, in a manner analogous to that shown in FIG. 7, programmaterial at a specified point in time can be located by converting thespecified time to a time T_(rel) relative to media data that representsthe program material. An index number is determined from time T_(rel)using, for example, an index duration. The index number is converted toa data position, thereby locating media data representing the programmaterial at the specified time T. The index duration may be the durationof one frame of media data. The index number may also be rounded tolocate an index boundary.

4. Media Stream Synchronization

Audio and video data typically have different frame rates, andtherefore, generally have different index rates. Thus, it is necessaryto correlate the audio data with the corresponding video data to ensurethat the audio and video remain synchronized. The media streamsynchronization method of the present invention ensures that the datafrom every series in a group starts out in synchrony, and remains insynchrony after any repositioning of the viewpoint within the programmaterial. Without synchronization, a viewer would perceive a time delayor offset between the video and the audio. In the preferred embodimentof the present invention, synchronization is done by correlating audioframes of the audio data with GOPs of the video data. As explained morefully below, this minimizes the offset between audio and video data inenvironments using GOPs. Likewise, closed-captioning text data may alsobe synchronized with GOPs of the video data in accordance with thepresent invention.

When jumping to various points in an item of program material, theindexing method of the present invention ensures that a jump is made tothe beginning of a GOP. To prevent audio data from being “out of sync”,it is necessary to correlate the corresponding audio data to each GOP.To do so, an index file for the video data is constructed first. Asdiscussed above with respect to FIG. 9, an index file for the video datawould contain repeated atom-relative byte positions for the frameswithin GOP1, repeated atom-relative byte positions for the frames withinGOF2, repeated atom-relative byte positions for the frames within GOP3,etc. Such a video data index file is then used to construct an indexfile for the corresponding audio data. An audio data index file isconstructed so that, for the set of audio frames that most closely spansthe time interval spanned by each GOP, each audio frame in that set isassigned the same atom-relative byte position. The assignedatom-relative byte position is the beginning of the set of audio frames.This synchronization method is illustrated in FIG. 9.

As shown in FIG. 9, GOP1 spans the time interval from t₁ to t₅. Audioframes A1, A2, A3, A4, and A5 (set I shown in FIG. 9) come closest tospanning this same time interval. In accordance with the synchronizationmethod of the present invention, audio frames A1, A2, A3, A4, and A5 areassigned unique index numbers, but each of these index numbers points tothe same atom-relative byte position that is the beginning of audioframe A1. Likewise, GOF2 spans the time interval from t₅ to t₈. Audioframes A6, A7, A8, and A9 (set II shown in FIG. 9) come closest tospanning this same time interval. In accordance with the synchronizationmethod of the present invention, audio frames A6 through A9 are assignedunique index numbers, but each of these index numbers points to the sameatom-relative byte position that is the beginning of audio frame A6. Thesame methodology would apply so that unique index numbers are assignedto audio frames A10-A15 (set III shown in FIG. 9), but each of theseindex numbers points to the same atom-relative byte position that is thebeginning of audio frame A10. The index numbers and correspondingatom-relative byte positions for the audio are thus selected to mostclosely match the GOP pattern in the corresponding video.

Using the synchronization method of the present invention, the offset or“out of sync” time between audio and video is generally held to bewithin one frame duration, typically approximately 1/30 sec. One frametime out of synchrony is within a tolerable limit because a decoder thatreceives program material from a media provider is typically capable ofresynchronizing such an offset. Without the synchronization method ofthe present invention, the offset time is typically on the order of oneGOP duration. Since GOPs can contain on the order of 15 frames, theoffset between audio and video without the synchronizing method of thepresent invention can be on the order of ½ sec. Such an offset is nottolerable because a decoder cannot resynchronize at the receiving end.Thus, the present invention helps ensure end-to-end synchrony.

The synchronization method described above may be used to correlate anytype and any number of atoms of data with each other for synchronizeddelivery to a viewer. FIG. 10 shows a flow diagram illustrating aprocess for synchronizing one or more auxiliary atoms containing mediadata with a base atom containing media data Referring now to FIG. 10, ina step 1005, a base atom containing media data is identified. In a step1007, one or more auxiliary atoms containing media data to besynchronized with the base atom media data are identified.

In a step 1010, a base atom index file is constructed that defines baseatom index boundaries for the base atom. By index boundary is meant alocation in the program material to which a viewer is permitted to jump,and at which atom-relative byte position changes to a different value.In the example illustrated in FIG. 9, the index boundaries for a baseatom containing MPEG-1 video data are the boundaries defined by theGOPs.

In a step 1015, an auxiliary atom index file is constructed for eachauxiliary atom by selecting auxiliary atom index boundaries that mostclosely match the base atom index boundaries in the base atom indexfile. In this manner, the media data contained in the auxiliary atoms issynchronized with the media data contained in the base atom. A group canthen be created from the base atom and auxiliary atoms. The programmaterial contained in such a group would be delivered to the viewer in asynchronized manner.

For example, a base atom may contain video data with the index fileconstructed so that the base atom index boundaries are Groups ofPictures (GOP) boundaries as described above. In such a scenario, one ofthe auxiliary atoms may contain corresponding audio data, and one of theauxiliary atoms may contain corresponding closed-captioning text data.An index file is created for the base atom video data. Index files arecreated for the audio data and closed-captioning text data by selectingthe index boundaries that most closely match the Groups of Picturesboundaries (index boundaries) of the base atom.

In another example, a base atom may contain MPEG-2 encoded audio andvideo data. In such a scenario, one of the auxiliary atoms may containthe corresponding closed-captioning text data. An index file is createdfor the base atom audio and video data. An index file is created for theclosed-captioning text data by selecting the index boundaries that mostclosely match the index boundaries of the MPEG-2 base atom data.

In an alternate embodiment, synchronization of audio data and video datacan be done “on the fly,” without constructing auxiliary atom indexfiles. In such an embodiment, the base atom index source is searched tolocate the next different atom-relative byte position. The index numberthat corresponds to that next different atom-relative byte position isconverted to an absolute time (e.g., T_(movie)). This absolute time isused to synchronize the auxiliary atoms to the base atom.

In a further embodiment, the present invention is directed to a computersystem for indexing media data for delivery to a viewer using theindexing method as described herein. Computer system 602 shown in FIG. 6is an exemplary computer system. As controllers of computer system 602,computer programs, software, or other computer control logic enablescomputer system 602 to deliver program material to a viewer from aspecified point in time, and in special modes such as pause, still,reverse, etc. Likewise, as controllers of computer system 602, computerprograms, software, or other computer control logic enables computersystem 602 to synchronize various types of atom data in accordance withthe synchronizing method described herein.

In yet a further embodiment, the present invention is directed to asystem that uses the object hierarchy and indexing and synchronizationmethods of the present invention for interactive delivery of programmaterial to a viewer. FIG. 11 shows a block diagram of such a system.Referring now to FIG. 11, a media delivery system 1100 for interactivedelivery of program material to a viewer is shown. Media delivery system1100 includes one or more servers 1102 connected by network 618.Computer system 602 represents one exemplary configuration for server1102, although other configurations for server 1102 may be used. In apreferred embodiment, servers 1102 are in a location remote from theviewer (viewer not shown).

Servers 1102 are also connected via a data communication or transfernetwork 1106 to one or more set-top computers 1112. Network 1106 caninclude, for example, microwave, satellite, cable, or telephone transfernetworks, or other types of networks suitable for data communication. Inan alternate embodiment, network 618 shown in FIG. 11 can be eliminatedso that servers 1102 communicate with each other through network 1106.

Each set-top computer 1112 is the interface between a television (notshown) and media delivery system 1100. A user or viewer controls set-topcomputer 1112 using a device such as a remote control 1110, therebyinteracting with media delivery system 1100 via set-top computer 1112.

In operation, a viewer's command is transmitted to set-top computer 1112via remote control 1110. Such a command may include, for example,selection of the content of program material (e.g., video, audio,closed-captioning text), or a movement command (e.g., skip to a selectedpoint in the program material or deliver program material in a specialmode such as slow-motion or reverse).

The viewer's command is transmitted from set-top computer 1112 via datacommunication network 1106 for receipt by remote server 1102. Media datarepresenting the program material is arranged in accordance with theviewer's command. For example, a group 218 of media data thatcorresponds to the viewer's selection of program material may becreated. As a further example, the viewer's command may be carried outby indexing to a location in a group 218 that corresponds to the pointselected by the viewer. As yet a further example, the viewer's commandmay be carried out by delivering a group 218 in a special mode, such asfast forward, reverse, etc.

The group 218 media data arranged in accordance with the viewer'scommand is transmitted from remote servers 1102 via data communicationnetwork 1106 to set-top computer 1112. The media data is then decoded,as necessary, by set-top computer 1112 for display on the viewer'stelevision.

In yet a further embodiment, the present invention is directed to asystem that uses the object hierarchy and indexing and synchronizationmethods of the present invention for interactive delivery of programmaterial to a workstation. FIG. 12 shows a block diagram of such asystem. Referring now to FIG. 12, a media delivery system 1200 forinteractive delivery to a workstation is shown. Media delivery system1200 includes one or more servers 1102 connected by network 618. Servers1102 are connected via a network 1204 to one or more workstations 1202.In a preferred embodiment, servers 1102 are in a location remote fromworkstations 1202. Network 1204 can include, for example, microwave,satellite, cable, telephone, or other types of networks suitable fordata communication. In an alternate embodiment, network 618 shown inFIG. 12 can be eliminated so that servers 1102 communicate with eachother through network 1204.

Workstations 1202 provide the interface between a workstation user (notshown) and media delivery system 1200. Each workstation preferablyincludes computer means that enable the workstation to perform thefollowing functions: to receive or input a command from the workstationuser; to transmit the command over network 1204 to servers 1102; toreceive program material from servers 1102; to display a video portionof the program material; and to audibly output an audio portion of theprogram material for the workstation user. Workstations 1202 may be inlocations different from each other.

Media delivery system 1200 is useful in an education environment forproviding educational program material to students at the workstations.Media delivery system 1200 is also useful in a business environment todistribute training material, technical or other business information toworkstations located throughout a company.

3. Conclusion

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. For example, the indexing andsynchronization methods of the present invention are not limited to theobject hierarchy described herein, or to any particular arrangement ofmedia data. Thus, the breadth and scope of the present invention shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

1. A method for locating program material at a specified time T,comprising: converting the specified time T to a time T_(rel), relativeto media data representing the program material; determining an indexnumber from said time T_(rel) using an index duration; converting saidindex number to a data position, thereby locating media datarepresenting the program material at the specified time T; andconverting a specified-segment relative time T_(seg) to a specified-atomrelative time T_(atom) by adding a specified segment's offset toT_(seg), and computing an index number from T_(atom) using an indexduration.
 2. The method of claim 1, wherein said index duration is aduration of one frame of media data.
 3. The method of claim 1, furthercomprising: rounding said index number to locate an index boundary. 4.The method of claim 3, wherein said index boundary is a beginning of aframe of media data.
 5. The method of claim 3, wherein said indexboundary is a beginning of a group of pictures of media data.
 6. Amethod as in claim 1, wherein the method for locating program materialcomprises locating the program material so that delivery of the programmaterial to a viewer via media delivery on demand begins at thespecified time T in the program material.
 7. A method as in claim 1,further comprising accessing a group having one or more series, eachseries having one or more segments that references a corresponding atomcontaining the media data representing the program material.
 8. A methodas in claim 7, further comprising determining in which specified segmentof which specified atom of media data the specified time T occurs.
 9. Amethod as in claim 8, further comprising converting the specified time Tto the specified-segment relative time T_(seg) by calculating an elapsedtime into the specified segment at which the specified time occurs. 10.A method as in claim 1, wherein an index file is used to correlate indexnumber with a corresponding data position.
 11. A method as in claim 10,wherein the corresponding data positions are the beginning of a frame ofmedia data, or the beginning of a group of media items of media data.12. A method as in claim 11, wherein the media items include pictures.13. A computer program product stored on a computer readable medium foruse with a computer system and a content on demand media delivery systemincluding computer readable program code for enabling a computer systemto carry out the locating of program material so that delivery of theprogram material to a viewer via media delivery on demand begins at thespecified time T in the program material; the computer program productincluding instructions for: converting the specified time T to a timeT_(rel) relative to media data representing the program material;determining an index number from said time T_(rel) using an indexduration; converting said index number to a data position, therebylocating media data representing the program material at the specifiedtime T; and converting a specified-segment relative time T_(seg) to aspecified-atom relative time T_(atom) by adding a specified segment'soffset to T_(seg), and computing an index number from T_(atom) using anindex duration.